The present invention relates to a structure of a gasified and melting furnace and an operation method thereof.
First, a furnace structure will be explained.
Conventional gasified/melting furnaces and ash melting furnaces have a freeboard for suppressing generation of tar and dioxin in a generated gas and for preventing dust scattering. Such a freeboard has been provided above a deposition layer formed in a furnace, as shown in FIG. 3.
However, the freeboard has some drawbacks since it occupies a broad space in the upper portion of the furnace.
First drawback is that the loading material such as waste must be loaded to the furnace from a feed opening provided in either diagonal upper portion or the top portion of the freeboard. When a material for adjusting components in the melt (hereinafter referred to as "component adjuster"), ash, and waste are loaded from the feed opening provided in the diagonal upper portion, they distribute in the furnace in different ways depending upon the difference in specific gravity. In other words, they distributes non-uniformly. Because of the non-uniform distribution, they are not mixed sufficiently, failing in adjustment of components. The resultant melt therefore increases in viscosity, so that stable discharge of the melt is not attained.
When waste is loaded from the feed opening provided in the top of the freeboard, as disclosed in Jpn. Pat. Appln. Publication No. 1-184314, small-sized materials of the loading waste tend to be scattered like a dust. As a result, the amount of disposal ash increases, raising a waste treatment cost, dramatically.
When an auxiliary fuel such as coke is loaded to a furnace as disclosed in Jpn. Pat. Appln. Publication No. 4-122486, it is loaded from a considerably higher position. There is a high possibility for the auxiliary fuel to be broken into pieces since it receives strong impact when it reaches the surface of the deposition layer. The spaces of the deposition layers for gas flow are filled with the resultant pieces. As a result, the auxiliary fuel will lose its original function.
There is another drawback. It is very difficult to measure the layer height of the deposition layer (here-inafter referred to as "layer height"), since the distance from the top of the freeboard to the surface of the deposition layer is very long.
To explain more specifically, since the freeboard portion has a high temperature and occupies a broad area right above the surface of the deposition layer, it is very difficult to measure the layer height through the freeboard. When the layer height is determined by a measuring device equipped with a weighted wire (often used in a powder-containing tank), a wire is easily broken with heat. When the layer height is determined by a measuring device with an electromagnetic wave or the like, the accuracy and steadiness of the measurement results are significantly low due to the long distance from the measuring device to the surface of the deposition layer. In addition, the measuring device mistakenly measures clinker grown in the furnace for the deposition layer. Likewise, the layer height cannot be measured stably without fail.